The UK would most likely join the US in fighting the regime if North Korea started a war, Trevor Taylor, professorial research fellow in defence management at the highly-respected Royal United Services Institute (RUSI) think tank, said.
He said if a war in the region started due to North Korean aggression then the UK would be “obliged” to support.
However, if the US started it, then the UK would be unlikely to join.
He told Express.co.uk: “If there was a protracted war in that area as a result of North Korean aggression then the Brits would feel obliged to support.
“If it was a very quick exchange we wouldn’t be there.
“I think it would depend very much on the nature of how a crisis arose and developed.
“If it was perceived what had taken place was American pre-empted action then it would be less likely the UK would feel it wanted to be involved.
“If it was perceived North Korea was acting in an aggressive way then it might be different.”
He tweeted: “Military solutions are now fully in place,locked and loaded,should North Korea act unwisely.
“Hopefully Kim Jong Un will find another path!”
Earlier this week erratic despot Kim announced he was planning an attack on the US Pacific territory of Guam.
Professor Taylor, added: “If there was a war in the region military people would want to offer options to the government but obviously the politics of all that would be pretty difficult.
“I think if in the event of unambiguous North Korea aggression that would make it more likely that the UK would feel obliged to, or feel pressured, to contribute, just as we did in 1950.
“But if the situation was more opaque and more ambiguous and owed something more to what the British public might feel was rather rash action by the United States than I don’t think they would want it.
“Parliament would certainly have a view.”
Mr Trump and Kim’s exchange is just the latest development in an ever-tightening spiral of threats and counter-threats from Washington and Pyongyang.
The US president repeated provocative threats to North Korea have been criticised by Washington heavyweights, including John McCain.
The former Republican presidential candidate hit out at Mr Trump, accusing him of having had his bluff called by Kim.
He said earlier this week: “I take exception to the President’s comments because you’ve got to be sure that you can do what you say you’re going to do.
“The great leaders I’ve seen don’t threaten unless they’re ready to act and I’m not sure President Trump is ready to act.”